Estimate a value between two known data points.
Linear interpolation assumes the relationship is straight between the two points, which is usually reasonable over a short span. The calculator flags when the target falls outside the known range. Interpolation is safe; extrapolation assumes the pattern continues, which is exactly the assumption that most often fails.
Linear Interpolation
y = y₁ + (x − x₁)(y₂ − y₁) ÷ (x₂ − x₁)
y = y₁ + (x − x₁)(y₂ − y₁) ÷ (x₂ − x₁) Linear interpolation assumes the relationship is straight between the two points, which is usually reasonable over a short span. The calculator flags when the target falls outside the known range.
Interpolation is safe; extrapolation assumes the pattern continues, which is exactly the assumption that most often fails.
This calculator takes 5 inputs: First x value, First y value, Second x value, Second y value, Target x value. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.